This invention relates to the explosive welding of tubes into tube sheets. It has particular applicability to the welding or otherwise bonding of aluminum tubes into steel alloy tube sheets. However, the techniques presented herein will also be applicable to other material combinations.
Previous devices for explosive welding of tubes into tube sheets have often included explosive charges placed within the tube near to flush alignment with the front face of the tube sheet. In addition, detonation cords or other means were positioned to contact and initiate detonation at the front face of the explosive charge. This type of arrangement causes the welding to begin at the front tube sheet face and proceed inwardly with possible gas pocket voids or poorly bonded portions of the weld resulting. In addition damage to outwardly facing portions of the tube and tube sheet may also occur. In some devices, blasting caps or detonators arranged near the tube sheet increased the risk of damage from explosion fragments.
In installations involving thin tube sheets, the gases resulting from the explosion can cause bulging and weakening of the tube beyond the rear or internal face of the tube sheet. This can be a substantial problem if sufficient restraints are not provided to prevent early displacement of the explosive cartridge and jetting of explosive gases towards and beyond the rear tube sheet face.
Therefore, in view of these disadvantages of prior art systems, it is an object of the present invention to provide an improved assembly for the explosive welding of tubes into a tube sheet in which the detonation of the explosive charge begins at an internal location and proceeds outwardly.
It is a further object to provide an explosive welding assembly in which bulging of tube portions beyond the rear tube sheet face are minimized.
It is also an object to provide an assembly for welding a tube into a tube sheet in which damage to the front tube and tube sheet faces from explosion fragments are minimized.